Connective tissue growth factor (CTGF) is a growth factor induced in fibroblasts by many factors, including TGF-β, and is essential for the ability of TGF-β to induce anchorage-independent growth (AIG), a property of transformed cells. CTGF was discovered in an attempt to identify the type of platelet-derived growth factor (PDGF) dimers present in the growth media of cultured endothelial cells, and is related immunologically and biologically to PDGF. See U.S. Pat. No. 5,408,040. CTGF also is mitogenic and chemotactic for cells, and hence growth factors in this family are believed to play a role in the normal development, growth, and repair of human tissue.
Seven proteins related to CTGF, including the chicken ortholog for Cyr61, CEF10, human, mouse, and Xenopus laevis CTGF, and human, chicken, and Xenopus laevis Nov have been isolated, cloned, sequenced, and characterized as belonging to the CCN gene family. Oemar and Luescher, Arterioscler. Thromb. Vasc. Biol., 17: 1483-1489 (1997). The gene encoding Cyr61 has been found to promote angiogenesis, tumor growth, and vascularization. Babic et al., Proc. Natl. Acad. Sci. USA, 95: 6355-6360 (1998). The nov gene is expressed in the kidney essentially at the embryonic stage, and alterations of nov expression, relative to the normal kidney, have been detected in both avian nephroblastomas and human Wilms' tumors. Martinerie et al., Oncogene, 9: 2729-2732 (1994). Wt1 downregulates human nov expression, which downregulation might represent a key element in normal and tumoral nephrogenesis. Martinerie et al., Oncogene, 12: 1479-1492 (1996). It has recently been proposed that the CTGF, nov, and cyr61 genes, which encode secreted proteins that contain conserved sequences and IGFBP motifs in their N-termini and bind IGFs with low affinity, represent more members of the IGFBP superfamily, along with the low-affinity mac25/IGFBP-7 (Yamanaka et al., J. Biol. Chem., 272: 30729-30734 (1997)) and the high-affinity IGFBPs 1-6. CTGF under this proposal would be designated IGFBP-8. Kim et al., Proc. Natl. Acad. Sci. USA, 94: 12981-12986 (1997).
The different members of the CCN family interact with various soluble or matrix associated macromolecules in particular sulfated glycoconjugates (Holt et al., J. Biol. Chem., 265:2852-2855 (1990)). This interaction was used to purify Cyr61 and CTGF by affinity chromatography on heparin-agarose (Frazier et al., J. Invest. Dermatol., 107:404-411 (1996); Kireeva et al., Mol. Cell. Biol., 16:1326-1334 (1996)). Cyr61 is secreted and associated with both the extracellular matrix and the cell surface due to its affinity for heparan sulfate (Yang et al., Cell. Growth Diff., 2:351-357 (1991)).
Recently, a protein was found in the mouse designated ELM1 that is expressed in low metastatic cells. Hashimoto et al., J. Exp. Med., 187: 289-296 (1998). The elm1 gene, a mouse homologue of WISP-1 disclosed below, is another member of the CTGF, Cyr61/Cef10, and neuroblastoma overexpressed-gene family and suppresses in vivo tumor growth and metastasis of K-1735 murine melanoma cells. Another recent article on rCop-1, the rat orthologue of WISP-2 described below describes the loss of expression of this gene after cell transformation. Zhang et al., Mol. Cell. Biol., 18:6131-6141 (1998).
CCN family members (with the exception of nov) are immediate early growth-responsive genes that are thought to regulate cell proliferation, differentiation, embryogenesis, and wound healing. Sequence homology among members of the CCN gene family is somewhat high; however, functions of these proteins in vitro range from growth stimulatory (i.e., human CTGF) to growth inhibitory (i.e., chicken Nov and also possibly hCTGF). Further, some molecules homologous to CTGF are indicated to be useful in the prevention of desmoplasia, the formation of highly cellular, excessive connective tissue stroma associated with some cancers, and fibrotic lesions associated with various skin disorders such as scleroderma, keloid, eosinophilic fasciitis, nodular fasciitis, and Dupuytren's contracture. Moreover, CTGF expression has recently been demonstrated in the fibrous stroma of mammary tumors, suggesting cancer stroma formation involves the induction of similar fibroproliferative growth factors as wound repair. Human CTGF is also expressed at very high levels in advanced atherosclerotic lesions, but not in normal arteries, suggesting it may play a role in atherosclerosis. Oemar and Luescher, supra.
Wnts are encoded by a large gene family whose members have been found in round worms, insects, cartilaginous fish, and vertebrates. Holland et al., Dev. Suppl., 125-133 (1994). Wnts are thought to function in a variety of developmental and physiological processes since many diverse species have multiple conserved Wnt genes. McMahon, Trends Genet., 8: 236-242 (1992); Nusse and Varmus, Cell, 69: 1073-1087 (1992). Wnt genes encode secreted glycoproteins that are thought to function as paracrine or autocrine signals active in several primitive cell types. McMahon, supra (1992); Nusse and Varmus, supra (1992). The Wnt growth factor family includes more than ten genes identified in the mouse (Wnt-1, -2, -3A, -3B, -4, -5A, -5B, -6, -7A, -7B, -8A, -8B, -10B, -11, -12, and -13) (see, e.g., Gavin et al., Genes Dev., 4: 2319-2332 (1990); Lee et al., Proc. Natl. Acad. Sci. USA, 92: 2268-2272 (1995); Christiansen et al., Mech. Dev., 51: 341-350 (1995)) and at least nine genes identified in the human (Wnt-1, -2, -3, -5A, -7A, -7B, -8B, -10B, and -11) by cDNA cloning. See, e.g., Vant Veer et al., Mol. Cell. Biol., 4: 2532-2534 (1984).
The Wnt-1 proto-oncogene (int-1) was originally identified from mammary tumors induced by mouse mammary tumor virus (MMTV) due to an insertion of viral DNA sequence. Nusse and Varmus, Cell, 31: 99-109 (1982). In adult mice, the expression level of Wnt-1 mRNA is detected only in the testis during later stages of sperm development. Wnt-1 protein is about 42 KDa and contains an amino-terminal hydrophobic region, which may function as a signal sequence for secretion (Nusse and Varmus, supra, 1992). The expression of Wnt-2/irp is detected in mouse fetal and adult tissues and its distribution does not overlap with the expression pattern for Wnt-1. Wnt-3 is associated with mouse mammary tumorigenesis. The expression of Wnt-3 in mouse embryos is detected in the neural tubes and in the limb buds. Wnt-5a transcripts are detected in the developing fore- and hind limbs at 9.5 through 14.5 days and highest levels are concentrated in apical ectoderm at the distal tip of limbs. Nusse and Varmus, supra (1992). Recently, a Wnt growth factor, termed Wnt-x, was described (WO95/17416) along with the detection of Wnt-x expression in bone tissues and in bone-derived cells. Also described was the role of Wnt-x in the maintenance of mature osteoblasts and the use of the Wnt-x growth factor as a therapeutic agent or in the development of other therapeutic agents to treat bone-related diseases.
Wnts may play a role in local cell signaling. Biochemical studies have shown that much of the secreted Wnt protein can be found associated with the cell surface or extracellular matrix rather than freely diffusible in the medium. Papkoff and Schryver, Mol. Cell. Biol., 10: 2723-2730 (1990); Bradley and Brown, EMBO J., 9: 1569-1575 (1990).
Studies of mutations in Wnt genes have indicated a role for Wnts in growth control and tissue patterning. In Drosophila, wingless (wg) encodes a Wnt-related gene (Rijsewik et al., Cell, 50: 649-657 (1987)) and wg mutations alter the pattern of embryonic ectoderm, neurogenesis, and imaginal disc outgrowth. Morata and Lawerence, Dev. Biol., 56: 227-240 (1977); Baker, Dev. Biol., 125: 96-108 (1988); Klingensmith and Nusse, Dev. Biol., 166: 396-414 (1994). In Caenorhabditis elegans, lin-44 encodes a Wnt homolog which is required for asymmetric cell divisions. Herman and Horvitz, Development, 120: 1035-1047 (1994). Knock-out mutations in mice have shown Wnts to be essential for brain development (McMahon and Bradley, Cell, 62: 1073-1085 (1990); Thomas and Cappechi, Nature, 346: 847-850 (1990)), and the outgrowth of embryonic primordia for kidney (Stark et al., Nature, 372: 679-683 (1994)), tail bud (Takada et al., Genes Dev., 8: 174-189 (1994)), and limb bud. Parr and McMahon, Nature, 374: 350-353 (1995). Overexpression of Wnts in the mammary gland can result in mammary hyperplasia (McMahon, supra (1992); Nusse and Varmus, supra (1992)), and precocious alveolar development. Bradbury et al., Dev. Biol., 170: 553-563 (1995).
Wnt-5a and Wnt-5b are expressed in the posterior and lateral mesoderm and the extraembryonic mesoderm of the day 7-8 murine embryo. Gavin et al., supra (1990). These embryonic domains contribute to the AGM region and yolk sac tissues from which multipotent hematopoietic precursors and HSCs are derived. Dzierzak and Medvinsky, Trends Genet., 11: 359-366 (1995); Zon et al., in Gluckman and Coulombel, ed., Colloque, INSERM, 235: 17-22 (1995), presented at the Joint International Workshop on Foetal and Neonatal Hematopoiesis and Mechanism of Bone Marrow Failure, Paris France, Apr. 3-6, 1995; Kanatsu and Nishikawa, Development, 122: 823-830 (1996). Wnt-5a, Wnt-10b, and other Wnts have been detected in limb buds, indicating possible roles in the development and patterning of the early bone microenvironment as shown for Wnt-7b. Gavin et al., supra (1990); Christiansen et al., Mech. Devel., 51: 341-350 (1995); Parr and McMahon, supra (1995).
The Wnt/Wg signal transduction pathway plays an important role in the biological development of the organism and has been implicated in several human cancers. This pathway also includes the tumor suppressor gene, APC. Mutations in the APC gene are associated with the development of sporadic and inherited forms of human colorectal cancer. The Wnt/Wg signal leads to the accumulation of beta-catenin/Armadillo in the cell, resulting in the formation of a bipartite transcription complex consisting of beta-catenin and a member of the lymphoid enhancer binding factor/T cell factor (LEF/TCF)HMG box transcription factor family. This complex translocates to the nucleus where it can activate expression of genes downstream of the Wnt/Wg signal, such as the engrailed and Ultrabithorax genes in Drosophila. 
For a review on Wnt, see Cadigan and Nusse, Genes & Dev., 11: 3286-3305 (1997).
Pennica et al., Proc. Natl. Acad. Sci., 95:14717-14722 (1998) describe the cloning and characterization of two genes, WISP-1 and WISP-2, that are up-regulated in the mouse mammary epithelial cell line C57MG transformed by Wnt-1, and a third related gene, WISP-3. Pennica et al. report that these WISP genes may be downstream of Wnt-1 signaling and that aberrant levels of WISP expression in colon cancer may play a role in colon tumorigenesis. WISP-1 has recently been identified as a β-catenin-regulated gene and the characterization of its oncogenic activity demonstrated that WISP-1 might contribute to β-catenin-mediated tumorigenesis (Xu et al., Gene & Develop., 14:585-595 (2000)). WISP-1 overexpression in normal rat kidney cells (NRK-49F) induced morphological transformation, accelerated cell growth and enhanced saturation density. In addition, these cells readily form tumors when injected into nude mice suggesting that WISP-1 may play some role in tumorigenesis (Xu et al., supra 2000).
Hurvitz et al., Nature Genetics, 23:94-97 (1999) describe a study involving WISP3 in which nine different mutations of WISP3 in unrelated individuals were found to be associated with the autosomal recessive skeletal disorder, progressive pseudorheumatoid dysplasia (PPD). WISP3 expression by RT-PCR was observed by Hurvitz et al. in human synoviocytes, articular cartilage chondrocytes, and bone-marrow-derived mesenchymal progenitor cells.
PCT application WO98/21236 published May 22, 1998 discloses a human connective tissue growth factor gene-3 (CTGF-3) encoding a 26 kD member of the growth factor superfamily. WO98/21236 discloses that the CTGF-3 amino acid sequence was deduced from a human osteoblast cDNA clone, and that CTGF-3 was expressed in multiple tissues like ovary, testis, heart, lung, skeletal muscle, adrenal medulla, adrenal cortex, thymus, prostate, small intestine and colon.
Several investigators have documented changes in the proteoglycan composition in neoplasms. Especially, a marked production of chondroitin sulfate proteoglycan is a well recognized phenomenon in a variety of malignant tumors. In addition, the expression of decorin, a dermatan sulfate containing proteoglycan, has been shown to be well correlated with malignancy in human carcinoma (Adany et al., J. Biol. Chem., 265:11389-11396 (1990); Hunzlemann et al., J. Invest. Dermatol., 104:509-513 (1995)). Recently, it was demonstrated that decorin suppresses the growth of several carcinomas (Santra 1997). Although the function of decorin in tumorigenic development is not fully understood, it was proposed that the decorin expression in the peritumorous stroma may reflect a regional response of the host connective tissue cells to the invading neoplastic cells (Stander et al., Gene Therapy, 5:1187-1194 (1999)).
For a recent review of various members of the connective tissue growth factor/cysteine-rich 61/nephroblastoma overexpressed (CNN) family, and their respective properties and activities, see Brigstock, Endocrine Reviews, 20:189-206 (1999).
Degenerative cartilagenous disorders broadly describe a collection of diseases characterized by degeneration or metabolic abnormalities of the connective tissues which can be manifested by pain, stiffness and limitation of motion of the affected body parts. The origin of these disorders can be, for example, pathological or as a result of trauma or injury.
Osteoarthritis (OA), also known as osteoarthrosis or degenerative joint disease, is typically the result of a series of localized degenerative processes that affect the articular structure and result in pain and diminished function. OA is often accompanied by a local inflammatory component that may accelerate joint destruction. OA is characterized by disruption of the smooth articulating surface of cartilage, with early loss of proteoglycans (PG) and collagens, followed by formation of clefts and fibrillation, and ultimately by full-thickness loss of cartilage. OA symptoms include local pain at the affected joints, especially after use. With disease progression, symptoms may progress to a continuous aching sensation, local discomfort and cosmetic alterations such as deformity of the affected joint.
In contrast to the localized nature of OA, rheumatoid arthritis (RA) is a systemic, inflammatory disease which likely begins in the synovium, the tissues surrounding the joint space. RA is a chronic autoimmune disorder characterized by symmetrical synovitis of the joint and typically affects small and large diarthrodial joints, leading to their progressive destruction. As the disease progresses, the symptoms of RA may also include fever, weight loss, thinning of the skin, multiorgan involvement, scleritis, corneal ulcers, formation of subcutaneous or subperiosteal nodules and premature death. While the cause(s) or origins of RA and OA are distinctly different, the cytokines and enzymes involved in cartilage destruction appear to be similar.
Peptide growth factors are believed to be important regulators of cartilage growth and cartilage cell (chondrocyte) behavior (i.e., differentiation, migration, division, and matrix synthesis or breakdown) F. S. Chen et al., Am J. Orthop. 26: 396-406 (1997). Growth factors that have been previously proposed to stimulate cartilage repair include insulin-like growth factor (IGF-1), Osborn, J. Orthop. Res. 7: 35-42 (1989); Florini & Roberts, J. Gerontol. 35: 23-30 (1980); basic fibroblast growth factor (bFGF), Toolan et al., J. Biomec. Mat. Res. 41: 244-50 (1998); Sah et al., Arch. Biochem. Biophys. 308: 137-47 (1994); bone morphogenetic protein (BMP), Sato & Urist, Clin. Orthop. Relat. Res. 183: 180-87 (1984); Chin et al., Arthritis Rheum. 34: 314-24 (1991) and transforming growth factor beta (TGF-beta), Hill & Logan, Prog. Growth Fac. Res. 4: 45-68 (1992); Guerne et al., J. Cell Physiol. 158: 476-84 (1994); Van der Kraan et al., Ann. Rheum. Dis. 51: 643-47 (1992).
Insulin-like growth factor (IGF-1) stimulates both matrix synthesis and cell proliferation in culture, K. Osborn. J. Orthop. Res. 7: 35-42 (1989), and insufficiency of IGF-1 may have an etiologic role in the development of osteoarthritis. R. D. Coutts, et al., Instructional Course Lect. 47: 487-94, Amer. Acad. Orthop. Surg. Rosemont, Ill. (1997). Some studies indicate that serum IGF-1 concentrations are lower in osteoarthritic patients than control groups, while other studies have found no difference. Nevertheless, both serum IGF-1 levels and chondrocyte responsiveness to IGF-1 decrease with age. J. R. Florini & S. B. Roberts, J. Gerontol. 35: 23-30 (1980). Thus, both the decreased availability of IGF-1 as well as diminished chondrocyte responsiveness to IGF-1 may contribute to cartilage homeostasis and lead to degeneration with advancing age.
IGF-1 has been proposed for the treatment of prevention of osteoarthritis. Intra-articular administration of IGF-1 in combination with sodium pentosan polysulfate (a chondrocyte catabolic activity inhibitor) caused improved histological appearance, and near-normal levels of degradative enzymes (neutral metalloproteinases and collagenase), tissue inhibitors of metalloproteinase and matrix collagen. R. A. Rogachefsky, et al., Ann. NY Acad. Sci. 732: 889-95 (1994). The use of IGF-1 either alone or as an adjuvant with other growth factors to stimulate cartilage regeneration has been described in WO 91/19510, WO 92/13565, U.S. Pat. No. 5,444,047, and EP 434,652,
Bone morphogenetic proteins (BMPs) are members of the large transforming growth factor beta (TGF-β) family of growth factors. In vitro and in vivo studies have shown that BMP induces the differentiation of mesenchymal cells into chondrocytes. K. Sato & M. Urist, Clin. Orthop. Relat. Res. 183: 180-87 (1984). Furthermore, skeletal growth factor and cartilage-derived growth factors have synergistic effects with BMP, as the combination of these growth factors with BMP and growth hormone initiates mesenchymal cell differentiation. Subsequent proliferation of the differentiated cells are stimulated by other factors. D. J. Hill & A Logan, Prog. Growth Fac. Res. 4: 45-68 (1992).
Transforming growth factor beta (TGF-β) is produced by osteoblasts, chondrocytes, platelets, activated lymphocytes, and other cells. R. D. Coutts et al., supra. TGF-β can have both stimulatory and inhibitory properties on matrix synthesis and cell proliferation depending on the target cell, dosage, and cell culture conditions. P. Guerne et al., J. Cell Physiol. 158: 476-84 (1994); H. Van Beuningen et al., Ann. Rheum. Dis. 52: 185-91 (1993); P. Van der Kraan et al., Ann. Rheum. Dis. 51: 643-47 (1992). Furthermore, as with IGF-1, TGF-β responsiveness is decreased with age. P. Guerne et al., J. Cell Physiol. 158: 476-84 (1994). However, TGF-β is a more potent stimulator of chondrocyte proliferation than other growth factors, including platelet-derived growth factor (PDGF), bFGF, and IGF-1 (Guerne et al., supra), and can stimulate proteoglycan production by chondrocytes. TGF-β also down-regulates the effects of cytokines which stimulate chondrocyte catabolism Van der Kraan et al., supra. In vivo, TGF-β induces proliferation and differentiation of mesenchymal cells into chondrocytes and enhances repair of partial-thickness defects in rabbit articular cartilage. E. B. Hunziker & L. Rosenberg, Trans. Orthopaed. Res. Soc. 19: 236 (1994).
While some investigators have focused on the use of certain growth factors to repair cartilage or chondrocyte tissue, others have looked at inhibiting the activity of molecules which induce cartilage destruction and/or inhibit matrix synthesis. One such molecule is the cytokine IL-1alpha, which has detrimental effects on several tissues within the joint, including generation of synovial inflammation and up-regulation matrix metalloproteinases and prostaglandin expression. V. Baragi, et al., J. Clin. Invest. 96: 2454-60 (1995); V. M. Baragi et al., Osteoarthritis Cartilage 5: 275-82 (1997); C. H. Evans et al., J. Keukoc. Biol. 64: 55-61 (1998); C. H Evans and P. D. Robbins, J. Rheumatol. 24: 2061-63 (1997); R. Kang et al., Biochem. Soc. Trans. 25: 533-37 (1997); R. Kang et al., Osteoarthritis Cartilage 5: 139-43 (1997). One means of antagonizing IL-1alpha is through treatment with soluble IL-1 receptor antagonist (IL-1ra), a naturally occurring protein that prevents IL-1 from binding to its receptor, thereby inhibiting both direct and indirect effects of IL-1 on cartilage. In mammals only one protease, named interleukin 1beta-convertase (ICE), can specifically generate mature, active IL-1alpha. Inhibition of ICE has been shown to block IL-1alpha production and may slow arthritic degeneration (reviewed in Martel-Pelletier J. et al. Front. Biosci. 4: d694-703). The soluble IL-1 receptor antagonist (IL-1ra), a naturally occurring protein that can inhibit the effects of IL-1 by preventing IL-1 from interacting with chondrocytes, has also been shown to be effective in animal models of arthritis and is currently being tested in humans for its ability to prevent incidence or progression of arthritis. Other cytokines, such as IL-1beta, tumor necrosis factor-alpha, interferon gamma, IL-6, and IL-8 have been linked to increased activation of synovial fibroblast-like cells, chondrocytes and/or macrophages. The inhibition of these cytokines may be of therapeutic benefit in preventing inflammation and cartilage destruction. Molecules which inhibit TNF-alpha activity have been shown to have beneficial effects on the joints of patients with rheumatoid arthritis.
Cartilage matrix degradation is believed to be due to cleavage of matrix molecules (proteoglycans and collagens) by proteases (reviewed in Woessner J F Jr., “Proteases of the extracellular matrix”, in Mow, V., Ratcliffe, A. (eds): Structure and Function of Articular Cartilage. Boca Raton, Fla., CRC Press, 1994 and Smith R. L., Front. In Biosci. 4:d704-712. While the key enzymes involved in matrix breakdown have not yet been clearly identified, matrix metalloproteinases (MMPs) and “aggrecanases” appear to play key roles in joint destruction. In addition, members of the serine and cysteine family of proteinases (for example, the cathepsins and urokinase or tissue plasminogen activator (uPA and tPA)) may also be involved. Plasmin, urokinase plasminogen activator (uPA) and tissue plasminogen activator (tPA) may play an important role in the activation pathway of the metalloproteinases. Evidence connects the closely related group of cathepsin B, L and S to matrix breakdown, and these cathepsins are somewhat increased in OA. Many cytokines, including IL-1, TNF-alpha and LIF induce MMP expression in chondrocytes. Induction of MMPs can be antagonized by TGF-β and IL-4 and potentiated, at least in rabbits, by FGF and PDGF. As shown by animal studies, inhibitors of these proteases (MMPs and aggrecanases) may at least partially protect joint tissue from damage in vivo.
Nitric oxide (NO) may also play a substantial role in the destruction of cartilage. Ashok et al., Curr. Opin. Rheum. 10: 263-268 (1998). Unlike normal cartilage which does not produce NO unless stimulated with cytokines such as IL-1, cartilage obtained from osteoarthritic joints produces large amounts of nitric oxide for over 3 days in culture despite the absence of added stimuli. Moreover, inhibition of NO production has been shown to prevent IL-1 mediated cartilage destruction and chondrocyte death as well as progression of osteoarthritis in animal models.